CHAPTER 11: DSTC
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 515
DES Values after Transfer End
The DES area can be saved when the OuterReload function is not used. If InnerReload is enabled for the
transfer address, OuterReload does not need to be enabled for the transfer address because the values
at the start of the transfer are stored in the DES. If neither OuterReload nor InnerReload is enabled, after
a transfer has ended, depending on the settings, values stored in the DES may be different from those
stored at the start of the transfer. In this situation, since the transfer cannot be started with the same DES
values, rebuild the DES via the CPU. The following explains how the values of the DES area are updated
after a transfer has ended.
The values of DES0 after the end of the transfer are the same as those at the start of the transfer, except
those of the DV[1:0] bits and ST[1:0] bits. In addition, the values of DES4, DES5 and DES6 after the end
of the transfer are the same as those at the start of the transfer.
The values of DES1 (transfer number counter) after the end of the transfer are updated according to the
values of MODE and ORL[0] at the start of the transfer as shown in Table 3-5. "X" in Table 3-5 indicates
that value has no effect on operation.
The value of IIN after the end of the transfer is the same as that at the start of the transfer. In the case of
ORL[0] = 0, the value of ORM is updated to 0x0001 and the value of IRM to "0x01" when a transfer ends
regardless of their values at the start of the transfer. However, if at the start of the transfer, the value of
ORM is not "0x0001" or the value of IRM is not 0x01, the value of ORM or the value of IRM is different
from what it was at the start of the transfer. Therefore, before restarting the transfer, rebuild the DES that
makes the DSTC rewrite ORM and IRM with necessary values via the CPU. Table 3-5 summarizes
conditions under which rebuilding DES1 becomes necessary.
Table 3-5 Values of DES1 at Transfer End and Necessity of Rebuilding DES1
The values of DES2 (transfer source address) after the end of the transfer are updated according to the
values of MODE, SAC[2:0] and ORL[1] of DES0 at the start of the transfer as shown in Table 3-6. "X" in
Table 3-6 indicates that value has no effect on operation. If the start value of DES2 is different from the
end value, rebuild DES2 before restart to transfer.
Table 3-6 Values of DES2 after Transfer End
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